GitLab

The eliminates non-public ash dependencies from the tests.

* Convert the tests to use the mojo system tray test API
* Clean up the test api, always use the same SystemTray*, remove some
  unnecessary RunLoop spins
* Put the tests on the mojo FYI bot. I'll move them to the main
  waterfall when I'm confident they are stable.

Bug: 775121
Test: browser_tests --mash --gtest_filter="SystemTrayClient*"
Change-Id: Id790ca77aa179db499c45825a1466e18cc9f78d7
Reviewed-on: https://chromium-review.googlesource.com/723604Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509596}